How do i figure the answer to this homework

You would need to find the least common denominator of the 2 denominators.  After you find it multiply the numerators by the number that gets you your least common denominator. For example , what is the least common denominator of 3 and 6? That would be of course 6. Now replace those denominators with 6.  3 times 2 makes the denominator 6 so also multiply 2 with what's on top the numerator 9 making you get 18.  Now, what gets you 6? for the first denomerator 6 times 1 gets you 6 so multiply the numerator by 1 to get you 1.  So, The answers we got is  and try to subtract them getting you 17/6 simplify that and you get 2 5/6. If you need more explaining comment down so I can try to make it simpler.

0.0078, 0.008, 0.077, 0.07